Tenants of a building closed for more than a month after the massive Midtown steam-pipe explosion say their offices were looted of laptop computers, iPods, cellphones, cash, booze and other items, The Post has learned.

“The whole incident is offensive on so many levels,” said Jeff Isler, president of Infographics, a graphics-arts company that had an estimated $45,000 worth of equipment stolen from its sixth-floor office at 370 Lexington Ave. “They looted us.”

Isler said that when he returned to his office in late August after being away for nearly six weeks, he found that more than 12 laptops, “every camera, every iPod, every video camera . . . every memory stick” had been stolen.

Also gone were the contents of Emergency-evacuation bags containing bottled water, flashlights and compasses that Isler’s father had bought for employees after 9/11.

“They were methodical,” Isler said of the looters.

Said Alan Schnurman, a lawyer who represents several tenants of 370 Lexington: “It’s almost like you are victimized twice. Not only are you a victim of this explosion, but you’re a victim of a burglary.”

It is not clear who committed the thefts, exactly when they occurred or how the crooks managed to get out of the building with the items.

370 Lexington was one of 11 buildings that were evacuated and temporarily closed in the wake of the July 18 explosion of a Con Ed steam pipe that sent a huge geyser of muck, water and steam spewing into the air.

Most of those buildings were reopened within several weeks, after authorities determined that there was no asbestos contamination in them, or that cleanups had removed that cancer-causing material.

But 370 Lexington – a 27-story, 300,000-square-foot building that sits on the corner of East 41st Street – remained closed until late August as a cleanup continued there. Tenants were not allowed to return to the building.

Roxanne Donovan, a spokeswoman for building owner Broad Street Development, said that for two weeks or so after the explosion, the landlord and its workers had no access to the building because it was under the control of city authorities.

During those two weeks, Donovan said, people from more than a half-dozen government entities, including the FDNY, NYPD, Office of Emergency Management, city Environmental Protection Department, Buildings Department, Health Department and U.S. Environmental Protection Agency, as well as workers from Con Ed and others, went into and out of the building.

When Broad Street was able to get back into the building after two weeks, the landlord found many office doors “busted open,” Donovan said.

After Broad Street regained access, it hired two companies – Degmor Inc. and The Par Group – to clean up the building and make sure it was free of asbestos before tenants were allowed to return on Aug. 24. Calls to Degmor and The Par Group for comment were not returned.

Elizabeth Clark, a Con Ed spokeswoman, said the utility’s workers “were in the building a total of three days to board up the windows to make the area safe and to facilitate the cleanup on the exterior of the building. We were accompanied by building-management employees on each occasion.”

NYPD spokesman Paul Browne said that, to date, “the Police Department has had a total of 14 complaints of stolen property, including electronics, cash and, in one instance, baseball memorabilia, during the course of the steam-pipe explosion and its aftermath.”

A police official said that of those 14 complaints, 11 were from people who had offices inside 370 Lexington Ave. Of those 11, eight were grand-larceny complaints and three petit-larceny claims, the official said.

Other tenants at 370 Lexington said they had not filed police reports but planned to.

“I’m not pointing fingers – yet,” said Cliff Seltzer, CEO of Puresend, when asked who might have looted his tech company’s office of five laptops, an iPod, computer-memory cards, several thousand dollars in cash, a camera, a DVD Player, an Apple TV box, a phone “and a few bottles of wine.”

He said he immediately called cops after returning to his office Aug. 24, for the first time since the explosion, and discovering the burglary.

Evelyn Galli, the chief operating officer of BCA Marketing Communications, said her ad agency’s office was looted of a laptop, two gift certificates for the Elizabeth Arden Red Door spa, “an expensive, hand-blown bottle containing rum from Jamaica,” as well as “a magnum of Dom Perignon [from] under my desk.”

“Now I’m sorry I didn’t drink it,” Galli said. George Stone, a lawyer, said thieves stole a Rolex belonging to another lawyer in his office as well as “a laptop and any cash that was around.”